CORAL REEFS. BY SARAH COOPER.

 The attention of seamen¹ and navigators has long been attracted by the number of circular islands in the warm parts of the Pacific and Indian oceans. Generally each one of these circular islands contains a lake of quiet water extending almost to its outer shores, so that the island looks like a fairy ring of land floating in the ocean, and adorned² with tropical trees and plants.

Happily for the boys and girls of the present day, this subject, with other equally fascinating branches of science, has now been studied by naturalists³, who give us the rich results of their labors⁴. It seems scarcely possible that the dainty beautiful corals which we examined not long ago in Young People can have anything to do with the making of islands, but so it is. Coral reefs are vast masses of coral which have grown in warm oceans. Their formation must have been slow, yet they sometimes extend hundreds of miles. Florida and many other parts of our solid continents are known to have been formed from coral reefs.

Let us now try to picture to ourselves the beginning of one of these reefs, and by following its growth step by step we may at least understand how it has been formed. There are hills and valleys on the bottom of the ocean as well as on the land. We will fancy that some young coral polyps which have been swimming about in the sea settle on the sides of one of these hills, and begin to grow and spread all around it. They will increase also by the deposit of eggs until they form a circular wall.

As the coral wall grows, the lower polyps and the inner ones die, their skeletons forming a solid foundation for all that grow above them. There may be only about an inch of living coral on the outside of the reef.

Fig⁵. 1.—a, a, Surface of the Water; b, Natural Red of the Ocean; c, c, Coral Formation; d, Lagoon⁶.

These walls rise nearly straight, and you will see that in doing so they inclose a circular basin of quiet water, and now you can understand why it is that a coral island mostly has a lake in the centre, as is shown in Fig. 1. The lakes are called lagoons⁷.

The bottom of the wall is formed of brain-coral and other solid kinds which live only in deep water, and they die when a certain height is reached. The formation of the new island does not stop with their death, however. The wall having now reached the proper height to suit branching corals, which require shallower water, their young polyps will settle upon it, and finish the structure. We might suppose a reef formed of branching corals would be open and unsubstantial, but in their growth the branches are thickly interlaced. The spaces between them become filled with substances floating in the ocean, and with pieces of coral which are broken from the reef by the fierce dashing of the waves. The whole forms a solid mass, stronger, perhaps, than any stone masonry⁸. The fragments of coral suffer no serious injury by breaking, but if lodged⁹ in some favorable spot they continue to grow.

The outer edge of the wall is steep and abrupt¹¹. Soundings taken just outside show very deep water. In this portion of the wall the corals live and thrive, always supplied with clear water. The breakers dash against it with such fury that apparently¹² the hardest rock must in time yield to the tremendous force of the waves. But, strange as it may appear, the soft jelly-like bodies of the polyps give to the reef the power of resisting the billows.

The inner surface of the wall slopes gently to the land, and being washed by quiet waters often containing sand and mud, it is not favorable to the growth of polyps. Still, there are certain kinds of coral which thrive within the lagoons; some of them are exceedingly brilliant and beautiful.

The coral polyps die before they reach the surface of the ocean, as no corals can live out of water. The remainder of the island is built up by shells, pieces of broken coral, sea-weed, and other floating materials which are washed upon it, raising the wall higher and higher. The never-ceasing action of the waves grinds up these shells and broken coral, until at last they form a soil of sand and mud which is now ready to receive any seeds that may float on the water or be brought by the winds and the birds. The seeds take root in the new soil, and young plants begin to appear on the glistening¹³ white surface. Floating cocoa-nuts often lodge¹⁰ on the shores, and cocoa-nut-trees are among the first to grow upon them. As the plants drop their leaves and decay, the soil is enriched little by little, and fitted for the home of various animals and birds, which in some mysterious manner find their way to these lonely spots far out at sea. In time our coral reef may become a beautiful tropical island fringed with waving trees and plants, and inhabited by man.

Fig. 2.—An Atoll.

Circular islands seldom form complete rings. There is generally an opening into the lake on the side most sheltered from the wind. A safe harbor in mid-ocean is thus made, in which vessels¹⁴ may take shelter, but it requires an expert navigator to pass the perils¹⁵ at its entrance. To anchor on the outer shore would be impossible. In Fig. 2 is a pretty little coral island with ships in its lagoon. If a lake is entirely¹⁶ inclosed by the coral wall, it may in time be changed to fresh water by the rains that fall into it.

Coral reefs often extend to a depth of three hundred feet below the surface of the ocean, and formerly¹⁷ persons were puzzled to know how they could have grown in such deep water, as no coral polyps can live at a greater depth than twenty or thirty fathoms¹⁸. This puzzling question was settled by the late Charles Darwin, who first showed that coral islands occur where there has been a gradual sinking of the bottom of the ocean. As the reef rises in height, the sinking of the foundation partly counteracts¹⁹ the upward growth of the coral; consequently the proper[Pg 21] depth of water is secured, and the reef appears to be stationary²⁰, whereas it is really growing upward.

Whenever a coral reef rises above the surface of the ocean, we may know that the coral, which grew under water, has been lifted above the level of the sea by a rising of the ocean-bed.

These circular reefs are called "atolls." They are quite different from the "fringing reefs," which extend along the shores of continents and islands. There are usually openings or breaks in fringing reefs directly opposite the mouths of rivers and fresh-water streams, as the corals can not endure currents which carry mud or sediment²¹. Perhaps the grandest reef to be found in any part of the world is the one extending along the northeast coast of Australia. It is nearly one thousand miles in length, and proves to us that the helpless coral polyps have played no trifling²² part in the formation of our earth. All they have accomplished²³ has been done merely by their living and growing.

1 seamen   

n.海员

参考例句：

• Experienced seamen will advise you about sailing in this weather. 有经验的海员会告诉你在这种天气下的航行情况。
• In the storm, many seamen wished they were on shore. 在暴风雨中，许多海员想，要是他们在陆地上就好了。

2 adorned   

[计]被修饰的

参考例句：

• The walls were adorned with paintings. 墙上装饰了绘画。
• And his coat was adorned with a flamboyant bunch of flowers. 他的外套上面装饰着一束艳丽刺目的鲜花。

3 naturalists   

n.博物学家( naturalist的名词复数 )；（文学艺术的）自然主义者

参考例句：

• Naturalists differ much in determining what characters are of generic value. 自然学者对于不同性状决定生物的属的含义上，各有各的见解。 来自辞典例句
• This fact has led naturalists to believe that the Isthmus was formerly open. 使许多自然学者相信这个地蛱在以前原是开通的。 来自辞典例句

4 labors   

v.努力争取(for)( labor的第三人称单数 )；苦干；详细分析；（指引擎）缓慢而困难地运转

参考例句：

• He was tiresome in contending for the value of his own labors. 他老为他自己劳动的价值而争强斗胜，令人生厌。 来自辞典例句
• Farm labors used to hire themselves out for the summer. 农业劳动者夏季常去当雇工。 来自辞典例句

5 fig   

n.无花果(树)

参考例句：

• The doctor finished the fig he had been eating and selected another.这位医生吃完了嘴里的无花果，又挑了一个。
• You can't find a person who doesn't know fig in the United States.你找不到任何一个在美国的人不知道无花果的。

6 lagoon   

n.泻湖，咸水湖

参考例句：

• The lagoon was pullulated with tropical fish.那个咸水湖聚满了热带鱼。
• This area isolates a restricted lagoon environment.将这一地区隔离起来使形成一个封闭的泻湖环境。

7 lagoons   

n.污水池( lagoon的名词复数 )；潟湖；（大湖或江河附近的）小而浅的淡水湖；温泉形成的池塘

参考例句：

• The Islands are by shallow crystal clear lagoons enclosed by coral reefs. 该群岛包围由珊瑚礁封闭的浅水清澈泻湖。 来自互联网
• It is deposited in low-energy environments in lakes, estuaries and lagoons. 它沉淀于湖泊、河口和礁湖的低能量环境中，也可于沉淀于深海环境。 来自互联网

8 masonry   

n.砖土建筑；砖石

参考例句：

• Masonry is a careful skill.砖石工艺是一种精心的技艺。
• The masonry of the old building began to crumble.旧楼房的砖石结构开始崩落。

9 lodged   

v.存放( lodge的过去式和过去分词 )；暂住；埋入；（权利、权威等）归属

参考例句：

• The certificate will have to be lodged at the registry. 证书必须存放在登记处。 来自《简明英汉词典》
• Our neighbours lodged a complaint against us with the police. 我们的邻居向警方控告我们。 来自《简明英汉词典》

10 lodge   

v.临时住宿，寄宿，寄存，容纳；n.传达室，小旅馆

参考例句：

• Is there anywhere that I can lodge in the village tonight?村里有我今晚过夜的地方吗？
• I shall lodge at the inn for two nights.我要在这家小店住两个晚上。

11 abrupt   

adj.突然的，意外的；唐突的，鲁莽的

参考例句：

• The river takes an abrupt bend to the west.这河突然向西转弯。
• His abrupt reply hurt our feelings.他粗鲁的回答伤了我们的感情。

12 apparently   

adv.显然地；表面上，似乎

参考例句：

• An apparently blind alley leads suddenly into an open space.山穷水尽，豁然开朗。
• He was apparently much surprised at the news.他对那个消息显然感到十分惊异。

13 glistening   

adj.闪耀的，反光的v.湿物闪耀，闪亮( glisten的现在分词 )

参考例句：

• Her eyes were glistening with tears. 她眼里闪着晶莹的泪花。
• Her eyes were glistening with tears. 她眼睛中的泪水闪着柔和的光。 来自《用法词典》

14 vessels   

n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人

参考例句：

• The river is navigable by vessels of up to 90 tons. 90 吨以下的船只可以从这条河通过。 来自《简明英汉词典》
• All modern vessels of any size are fitted with radar installations. 所有现代化船只都有雷达装置。 来自《现代汉英综合大词典》

15 perils   

极大危险( peril的名词复数 )； 危险的事（或环境）

参考例句：

• The commander bade his men be undaunted in the face of perils. 指挥员命令他的战士要临危不惧。
• With how many more perils and disasters would he load himself? 他还要再冒多少风险和遭受多少灾难？

16 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。

17 formerly   

adv.从前，以前

参考例句：

• We now enjoy these comforts of which formerly we had only heard.我们现在享受到了过去只是听说过的那些舒适条件。
• This boat was formerly used on the rivers of China.这船从前航行在中国内河里。

18 fathoms   

英寻( fathom的名词复数 )

参考例句：

• The harbour is four fathoms deep. 港深为四英寻。
• One bait was down forty fathoms. 有个鱼饵下沉到四十英寻的深处。

19 counteracts   

对抗，抵消( counteract的第三人称单数 )

参考例句：

• The drug counteracts the effects of the poison. 这种药可抵消毒物的作用。
• Offset Something that balances, counteracts, or compensates the effects of another thing. 弥补用来平衡、抵消或偿还另一财物的东西。

20 stationary   

adj.固定的，静止不动的

参考例句：

• A stationary object is easy to be aimed at.一个静止不动的物体是容易瞄准的。
• Wait until the bus is stationary before you get off.你要等公共汽车停稳了再下车。

21 sediment   

n.沉淀，沉渣，沉积(物)

参考例句：

• The sediment settled and the water was clear.杂质沉淀后，水变清了。
• Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。

22 trifling   

adj.微不足道的；没什么价值的

参考例句：

• They quarreled over a trifling matter.他们为这种微不足道的事情争吵。
• So far Europe has no doubt, gained a real conveniency,though surely a very trifling one.直到现在为止,欧洲无疑地已经获得了实在的便利，不过那确是一种微不足道的便利。

23 accomplished   

adj.有才艺的；有造诣的；达到了的

参考例句：

• Thanks to your help,we accomplished the task ahead of schedule.亏得你们帮忙,我们才提前完成了任务。
• Removal of excess heat is accomplished by means of a radiator.通过散热器完成多余热量的排出。